Major
Amitriptyline × Haloperidol
Tricyclic antidepressants (TCA)×First-generation antipsychotics. Butyrophenone derivatives
Mechanism
Additive QT prolongation and anticholinergic effect. Both drugs are sedating. In elderly patients with dementia, severe delirium and arrhythmias have been reported.
Symptoms
Drowsiness, sedation, confusion, delirium (especially in older patients). Dry mouth, constipation, urinary retention. QT prolongation on ECG with torsades de pointes risk.
Management
Avoid the combination, especially in older patients. Alternative antipsychotics with minimal QT effect: olanzapine or aripiprazole. Alternative antidepressants without QT effect: mirtazapine or agomelatine.